Titanium dioxide superfine particles and method for producing the same

Abstract

It is an object to provide a method for producing titanium dioxide superfine particles, which produces monodispersed titanium dioxide superfine particles depending on its purpose, causes no clogging with a product due to self-dischargeability, requires no great pressure, and is excellent in productivity. In the method for producing titanium dioxide superfine particles in a fluid containing a titanium compound by separation, the fluid is formed into a thin film fluid between two processing surfaces arranged so as to be able to approach to and separate from each other, at least one of which rotates relative to the other, and the titanium dioxide superfine particles are separated in the thin film fluid.

The invention claimed is: 
     
       1. A method for producing titanium dioxide superfine particles, the method comprising the steps of:
 providing two processing surfaces arranged so as to be able to approach to and separate from each other, at least one of two processing surfaces rotating relative to the other; 
 providing at least one fluid, as fluid to be processed, containing a titanium compound, the at least one fluid not containing titanium dioxide superfine particles; 
 forming the at least one fluid into a thin film fluid between the two processing surfaces; and 
 producing and separating titanium dioxide superfine particles in the thin film fluid between the two processing surfaces, 
 wherein the produced and separated titanium dioxide superfine particles are crystal forms, amorphous or mixtures thereof. 
 
     
     
       2. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein at least one of the fluids contains a dispersant. 
     
     
       3. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein the titanium compound is at least one selected from tetraalkoxy titanium, titanium tetrachloride, titanyl sulfate, titanium citrate and titanium tetranitrate. 
     
     
       4. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein besides the titanium compound, a compound containing an element forming a solid solution in titanium dioxide is contained in at least one of the fluids. 
     
     
       5. The method for producing titanium dioxide superfine particles according to  claim 4 , wherein the compound containing an element forming a solid solution in titanium dioxide is at least one selected from alkoxides having Al, Ba, Mg, Ca, La, Fe, Si, Zr, Pb, Sn, Zn, Cd, As, Ga, Sr, Bi, Ta, Se, Te, Hf, Ni, Mn, Co, S, Cr, V, Ge, Li or B, or salts thereof. 
     
     
       6. The method for producing titanium dioxide superfine particles according to  claim 2 , wherein the dispersant is at least one selected from the group consisting of polymer dispersion stabilizers, nonionic surfactants, anionic surfactants, amphoteric surfactants, high-molecular organic acids, high molecular organic matters, and sodium diisooctyl sulfosuccinate (AOT). 
     
     
       7. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein a pH adjusting agent is added to at least one of the fluids. 
     
     
       8. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein hydrogen peroxide is added to at least one of the fluids. 
     
     
       9. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein at least one diol or triol selected from ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanedial, 2-butene-1,4-diol, hexylene glycol, octylene glycol, glycerin, hexaglycerol, and 1,2,6-hexanetriol is added to at least one of the fluids. 
     
     
       10. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein both or either of a mixture and a solid solution of glass containing both or either of silicon oxide and silicon and a substance containing at least one of silicon-containing composite oxide is dissolved in at least one of hydrochloric acid, sulfuric acid and nitric acid, and the resultant is added to at least one of the fluids. 
     
     
       11. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein a chlorine ion-containing acid is added to at least one of the fluids, and then a Bronsted base is added to said fluid that the acid has been added to or to a fluid other than the fluid. 
     
     
       12. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein an oxide and an organometallic compound that contains at least one selected from aluminum, zirconium, antimony, tin, zinc and titanium, are added to at least one of the fluids. 
     
     
       13. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein non-resin electrification regulators or electrification regulators are added to at least one of the fluids. 
     
     
       14. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein, besides the titanium compound, calcium carbonate and phosphoric acid, or hydroxyapatite is contained in at least one of the fluids. 
     
     
       15. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein the production method comprises:
 a fluid pressure imparting mechanism for imparting pressure to a fluid to be processed, 
 at least two processing members of a first processing member and a second processing member, the second member being capable of approaching to and separating from the first processing member, and 
 a rotation drive mechanism for rotating the first processing member and the second processing member relative to each other, 
 wherein each of the processing members is provided with at least two processing surfaces of a first processing surface and a second processing surface disposed in a position they are faced with each other; 
 wherein each of the processing surfaces constitutes part of a sealed flow path through which the fluid under the pressure is passed; 
 wherein two or more fluids to be processed, at least one of which contains a reactant, are uniformly mixed and positively reacted between the processing surfaces; 
 wherein of the first and second processing members, at least the second processing member is provided with a pressure-receiving surface, and at least part of the pressure-receiving surface is comprised of the second processing surface, 
 wherein the pressure-receiving surface receives pressure applied to the fluid by the fluid pressure imparting mechanism thereby generating a force to move in the direction of separating the second processing surface from the first processing surface, 
 wherein the fluid under the pressure is passed between the first and second processing surfaces being capable of approaching to and separating from each other and rotating relative to each other, whereby the fluid under the pressure forms a thin film fluid while passing between both the processing surfaces; and further comprises: 
 another introduction path independent of the flow path through which the fluid to be processed under the pressure is passed, and 
 at least one opening leading to the separate introduction path and being arranged in at least either the first processing surface or the second processing surface, wherein at least one fluid to be processed sent from the separate introduction path is introduced into between the processing surfaces, whereby said thin film fluid is formed, wherein the reactant contained in at least any one of the aforementioned fluids to be processed, and a fluid other than said fluids to be processed enable a state of desired reaction by mixing under uniform stirring in the fluid film. 
 
     
     
       16. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein heat is added between the processing surfaces; or ultraviolet ray (UV) is irradiated between the processing surfaces; or ultrasonic energy is supplied between the processing surfaces. 
     
     
       17. The method for producing titanium dioxide superfine particles according to  claim 1 , wherein the obtained titanium dioxide superfine particles have a volume-average primary particle size of 0.5 nm to 1000 nm and re-dispersibility. 
     
     
       18. The method for producing titanium dioxide superfine particles according to  claim 1 , comprising:
 providing a fluid pressure imparting mechanism for imparting pressure to the at least one fluid to be processed, 
 providing at least two processing members of a first processing member and a second processing member, the second member being capable of approaching to and separating from the first processing member, and 
 providing a rotation drive mechanism for rotating the first processing member and the second processing member relative to each other, 
 wherein each of the processing members is provided with at least two processing surfaces of a first processing surface and a second processing surface disposed in a position they are faced with each other; 
 wherein each of the processing surfaces constitutes part of a sealed flow path through which the pressure-imparted fluid is passed; 
 wherein, of the first and second processing members, at least the second processing member is provided with a pressure-receiving surface, and at least part of the pressure-receiving surface is comprised of the second processing surface, 
 wherein the pressure-receiving surface receives pressure applied to the fluid by the fluid pressure imparting mechanism thereby generating a force to move in the direction of separating the second processing surface from the first processing surface, 
 wherein the pressure-imparted fluid is passed between the first and second processing surfaces being capable of approaching to and separating from each other and rotating relative to each other, whereby the fluid forms said thin film fluid while passing between both the processing surfaces, and the titanium dioxide superfine particles are produced and separated in the thin film fluid. 
 
     
     
       19. The method for producing titanium dioxide superfine particles according to  claim 1 ,
 wherein each of the processing surfaces constitutes part of a sealed flow path through which the at least one fluid to be processed is passed, and another introduction path independent of the flow path through which the at least one fluid to be processed is passed is provided, and at least one opening leading to the introduction path and being arranged in at least either of the processing surfaces, and 
 wherein a second fluid to be processed sent from the introduction path, the second fluid being other than said fluid to be processed, is introduced into between the processing surfaces, whereby said thin film fluid is formed. 
 
     
     
       20. A method for producing titanium dioxide superfine particles, wherein at least two fluids are used, the method comprising the steps of:
 providing the at least two fluids, at least one of the at least two fluids being a fluid containing at least one titanium compound, the at least two fluids not containing titanium dioxide superfine particles; 
 providing two processing surfaces arranged so as to be able to approach to and separate from each other, at least one of two processing surfaces rotating relative to the other; 
 forming the at least two fluids into a thin film fluid between the two processing surfaces; and 
 producing and separating titanium dioxide superfine particles in the thin film fluid between the two processing surfaces, 
 wherein the produced and separated titanium dioxide superfine particles are crystal forms, amorphous or mixtures thereof. 
 
     
     
       21. A method for producing titanium dioxide superfine particles, wherein at least two fluids are used, the method comprising the steps of:
 providing the at least two fluids, wherein at least one of the at least two fluids is a reverse micellar solution in which a dispersant and water are added to an organic solvent, and at least one of the at least two fluids is any one of a nonaqueous solution containing a titanium compound, an aqueous solution containing a titanium compound and a reverse micellar solution containing a titanium compound, and the at least two fluids not containing titanium dioxide superfine particles; 
 providing two processing surfaces arranged so as to be able to approach to and separate from each other, at least one of two processing surfaces rotating relative to the other; 
 forming the at least two fluids into a thin film fluid between the two processing surfaces; and 
 producing and separating titanium dioxide superfine particles in the thin film fluid between the two processing surfaces, 
 wherein the produced and separated titanium dioxide superfine particles are crystal forms, amorphous or mixtures thereof.